Die hemming assembly and method

ABSTRACT

A hemming assembly and method for joining the edges of a pair of panels together includes a main die supporting edges of the two panels. The main die-containing hemming fixture can be stationary with the pre-hem and final hem dies moving, or the main die can move and the pre-hem and final hem dies can remain stationary during hemming. A pre-hem slide supporting a pre-hem tool at an angle to the tool fixture supporting both the final die holder and the slide. For table top applications, the hemming fixture uses guide mechanisms to control travel of the pre-hem slide and tool fixture. The hemming fixture is also movable with respect to an assembly drive to facilitate different hemming operations.

[0001] This application is a continuation-in-part application based on application Ser. No. 09/793,422 filed on Feb. 27, 2001.

FIELD OF THE INVENTION

[0002] The present invention is directed to a die hemming assembly and method, and in particular to a hemming assembly and method that utilize a vertical motion as part of the pre-hemming operation.

BACKGROUND ART

[0003] In the prior art, it is well known to join together a pair of preformed parts into a single unitary structure. This joining is particularly prevalent in the automotive industry where a component such as a hollow door, hood, deck gate, end gate, trunk lid or the like is formed using these joining techniques. Typically, these components comprise an outer and an inner panel. The edges of the panels are clinched together using a hemming machine or apparatus.

[0004] A widely-used process for hemming of door panels involves a pre-hemming step followed by a final hemming step. In the pre-hemming step, an upstanding or right-angled flange of one panel is bent over a flat edge of another panel by a pre-hemming die surface. In the final hemming step, the bent flange is flattened onto the flat edge of the other panel to form the hem using a final hemming die surface.

[0005] Various types of machines have been proposed to perform these types of hemming operations. One type uses a vertically-driven main die and a horizontally-driven hem gate. The hem gate supports the pre-hemming and final hemming die surfaces and is moved laterally or horizontally for hemming. The main die is raised vertically for the hemming steps. These horizontally-driven gates lack accuracy and repeatability in the hemming process. In these machines, there are typically four separate assemblies to hem each side of a rectangular or square unit. Since each assembly may have its own main die and drive for the hemmers, the overall apparatus is rather clumsy and bulky.

[0006] Another type of hemming machine uses a linkage and a swing-type motion to allow the pre-hemming and final hemming surfaces to contact the flange for hemming. The complicated drive mechanisms associated with these machines make them expensive and can cause unwanted variations over time in hemming performance.

[0007] Another hemming apparatus is disclosed in U.S. Pat. No. 5,150,508 to St. Denis. This patent discloses a hemming machine using the horizontally-driven hem gate and vertically-driven main die described above. In St. Denis, the main die is raised hydraulically between two positions for pre-hemming and final hemming. A lifter is used to then remove the hemmed part or load a unit to be hemmed. This machine also suffers from the drawbacks noted above.

[0008] Another problem with present day hemming apparatus that employ a swinging mechanism for pre-hemming is distortion to the panel. Referring now to FIGS. 1a and 1 b, a pre-hemming operation is schematically depicted wherein panel 1 is hemmed to panel 3 using die 2. The arrow in FIG. 1a represents the motion of the pre-hemming tool (not shown), which would contact the end portion 5 of panel 1. FIG. 1b shows the panels in the pre-hemmed state with the end portion 5 bent over the edge 7 of the panel 2. Reference numeral 9 shows that lifting and distortion can occur at the bend 11 when the end portion is pre-hemmed using a swinging motion from the pre-hem tool. This lifting and distortion compromises the quality of the hemmed panels, and can result in part rejection.

[0009] In light of the disadvantages of prior art hemming machines, particularly the distortion at the hemmed edge when using swinging or arcuate pre-hemming motions, a need has developed to provide improved hemming apparatus and methods. The present invention responds to this need by providing a hemming apparatus employing a pre-hemming mechanism that employs a vertical pre-hemming action, and a pre-hemming mechanism that also cooperates with a vertical final hemming action.

SUMMARY OF THE INVENTION

[0010] It is a first object of the present invention to provide an improved hemming apparatus.

[0011] Another object of the present invention is to provide an improved method of hemming parts together.

[0012] Yet another object of the invention is a hemming apparatus employing a mechanism utilizing a generally vertical force for pre-hemming.

[0013] A further object of the invention is a method of hemming panels together wherein pre-hemming is primarily accomplished by a generally vertical action rather than a horizontal or arcuate motion.

[0014] A still further object of the invention is the ability to incorporate a number of pre-hemming and final hemming operations in sequence using a single downward motion of the hemming apparatus.

[0015] Other objects and advantages of the present invention will become apparent as a description thereof proceeds.

[0016] In satisfaction of the foregoing objects and advantages, the present invention provides a die hemming assembly which is improved over prior art types utilizing arcuate pre-hemming motion. The assembly includes components that make up a hemming apparatus, the apparatus adapted for hemming an upstanding edge of a first panel to an edge of a second panel to form a joint. The assembly includes a main die supporting the first and second panels, a pre-hem slide supporting a pre-hem tool that has an angled tool surface, and a final hem die holder supporting a final hem tool. A guide mechanism is in engagement with the pre-hem slide to direct the pre-hem slide along a first path generally vertical to the upstanding edge and along a second path angled with respect to vertical. At least one drive directs the pre-hem slide along the first and second paths and directs the final hem die holder along a generally vertical path. One drive can move both the pre-hem tool and the final hem die, either together or sequentially, or each can have their own drive.

[0017] A number of assemblies can be arranged together to hem a number of different edges, either in sequence or simultaneously. The various tools and dies can be appropriately spaced so that, if desired, one press or downward motion cycle can hem all the desired edges.

[0018] In one embodiment, the guide mechanism comprises an elongated element having at least one vertical guide surface and at least one angled guide surface. The pre-hem slide has at least one complementary vertical guide surface and at least one complementary angled guide surface. Movement of the at least one complementary vertical guide surface of the pre-hem slide against the at least one vertical guide surface of the guide member directs the pre-hem tool generally vertically against the upstanding edge for at least a partial pre-hemming. Movement of the at least one complementary angled guide surface of the pre-hem slide against the at least one angled guide surface of the guide member angles the pre-hem tool away from the pre-hemmed edge to complete pre-hemming or permit final hemming.

[0019] The guide mechanism of this embodiment includes a horizontal guide to maintain a horizontal orientation of the pre-hem slide during angling movement. The horizontal guide can be a rail linked to the drive, and a set of roller bearings or the like linked to the pre-hem slide. The bearing follow in the rail as the pre-hem slide angles away from the edges to maintain the pre-hem slide in its horizontal orientation.

[0020] The main die is supported by a base, which with the main die forms a space to receive the pre-hem slide during its angled movement, thus allowing exposure of the pre-hemmed edges for final hemming.

[0021] The invention also entails a method of hemming at least one upstanding edge of one panel to the edge of another panel, whereby the upstanding edge is at least partially pre-hemmed by contacting the upstanding edge with a pre-hem tool that follows a generally vertical path. Completion of the pre-hemming can be accomplished by additional travel of the pre-hem tool along the vertical path, or by the pre-hem tool as it angles away from the edges to permit final hemming. Final hemming occurs by a final die traveling along a vertical path as well.

[0022] In one mode, the pre-hem tool is mounted on a slide body, and the slide body moves vertically and then at an angle as part of the pre-hemming and final hemming operations.

[0023] Once the pre-hemming and final hemming steps are complete, the die holder and pre-hem slide are moved back to their respective start positions to start the cycle all over again. A number of hemming operations can be performed in sequence using a number of the assemblies, whereby the pre-hem slides and final die holders would be arranged and spaced vertically apart so that a single downward stroke of the apparatus would complete the pre-hemming and final hemming for a number of edges of a pair of panels.

[0024] In a further embodiment, the pre-hem slide can be supported to move at an angle with respect to the upper platen, and can be biased in a pre-hemming orientation using a spring or spring-like mechanism rather than a vertical guide surface.

[0025] Another improvement involves a table top application. The table top application can employ the pre-hem slide that moves with an angle with respect to the tool fixture or upper platen. The apparatus of this embodiment comprises a pre-hemming tool holder supporting a pre-hem tool and a mechanism to first guide the pre-hemming tool holder along a generally vertical travel path for at least a partial pre-hemming of the edges. The mechanism also guides the pre-hemming tool along a generally horizontal path or a path having an upward angle by contact between a stationary guide surface and a surface on a pre-hem slide supporting the pre-hemming tool to expose the pre-hemmed edges for one of final hemming or completion of pre-hemming and final hemming.

[0026] The method of this improvement comprises at least partially pre-hemming the edges together by first guiding a pre-hemming tool generally vertically against the upstanding edge, and then moving the pre-hemming tool either horizontally or at an upward angle away by contact between a guide surface on a pre-hem slide supporting the pre-hemming tool a stationary guide surface to expose the pre-hemmed edges for one of final hemming or completion of pre-hemming and final hemming. The pre-hem slide can move vertically or at an upward angle after pre-hemming, and can be biased by a spring or the like during the pre-hemming operation.

[0027] The tool fixture supporting the pre-hem and final hem dies can translate laterally with movement of the power source driving the main die. This allows the tools to be positioned for hemming, and moved laterally out of the way for panel changing. The main die and hemming tools can be swapped out with another hemming fixture by an unlocking of the hemming fixture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Reference is now made to the drawings of the invention wherein:

[0029]FIGS. 1a and 1 b are schematic representations of a prior art pre-hemming operation;

[0030]FIG. 2 is a schematic view of one embodiment of the hemming apparatus;

[0031]FIGS. 3a-d show a conventional pre-hem and final hem cycle using the apparatus of FIG. 2;

[0032]FIGS. 4a and 4 b show exemplary pre-hem cycles using the apparatus of FIG. 2;

[0033]FIGS. 5a-e show a sequential hemming cycle of a pair of edges of one panel to another panel;

[0034]FIGS. 6a and 6 b show a first alternative mechanism for the pre-hemming mechanism of FIG. 2;

[0035]FIGS. 7a and 7 b shows a second alternative for the FIG. 2 pre-hemming mechanism;

[0036]FIG. 8 is yet another pre-hemming mechanism;

[0037]FIG. 9 is an alternative mechanism for horizontal guiding of the pre-hemming tool;

[0038]FIG. 10 is another alternative horizontal guiding mechanism;

[0039]FIG. 11 is schematic view of another embodiment of the invention employing a modified pre-hem slide;

[0040]FIGS. 12a-12 c are schematic representations of the operation of the FIG. 11 embodiment;

[0041]FIGS. 13a-13 c are additional schematic representations of the operation of the FIG. 11 embodiment;

[0042]FIG. 14 shows yet another embodiment of the invention using a table top arrangement;

[0043]FIGS. 15a-d show the operation of the FIG. 14 embodiment;

[0044]FIG. 16 shows a schematic top view of a plurality of the hemming apparatus of FIG. 14 surrounding a main die ring;

[0045]FIG. 17 shows a schematic view of the assembly for moving a hemming fixture of the FIG. 14 embodiment; and

[0046]FIG. 18 shows a top schematic view of components of the assembly of FIG. 17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The present invention offers significant advantages in the field of hemming parts together, particularly automotive parts. The invention overcomes the problems of distortion and poor-quality hems when using methods and apparatus that impart an arcuate, or swinging motion to the pre-hem tool as part of a pre-hemming operation. The invention allows for the hemming of panels without the need for using such motions. In addition, the inventive apparatus produces a superior hem joint since the pre-hemming motion is a generally vertical one, and a constant downward pressure can be maintained during the hemming cycle.

[0048] In addition, the unique pre-hemming apparatus and method offers enhanced flexibility in terms of operating a number of the apparatus in groupings to accommodate the panels or parts being edged. Further, the pre-hem apparatus can be arranged with the final hem mechanism so that the hemming process can be completed in a single press cycle. The final hemming could be operated sequentially to match the cycle(s) of pre-hemming to assure that only one downward motion is needed to complete both pre-hemming and final hemming.

[0049] The inventive hemming apparatus and method are especially suited for joining panels as part of vehicle manufacture, e.g., cars and truck manufacture, but the apparatus and methodology can be used to join any panels together wherein a tight and lasting joint is required.

[0050]FIG. 2 shows one example of an apparatus employing the features of the invention. However and as will be explained below, other mechanisms than those illustrated could be employed to effect the pre-hem as well as the final hem cycles that practice the invention.

[0051]FIG. 2 is a schematic representation of one embodiment of the invention wherein the overall apparatus is generally designated by the reference numeral 20. The apparatus includes a main die and base assembly 21, that provides support for the two portions of panels 23 and 25 intended to be hemmed together.

[0052] The assembly 21 is configured with a space 27 to allow travel of a pre-hem slide 29 as explained below. The assembly 21 also supports a main die 31, which aids in forming the hem or joint between the two panels 23 and 25. It should be understood that the assembly configuration, including die shape, mounting, etc. may vary depending on the particular hemming operation to be performed, and further details of these known features is not necessary for understanding of the invention. However, the configuration should allow for the travel of the pre-hem slide 29 as explained below.

[0053] The pre-hem slide 29 comprises a slide body 33, the body supporting a pre-hem tool 35. The tool 35 has an angled tool surface 37, preferably angled at 40-50°, more preferably 45°, for hemming as will be described below.

[0054] In the embodiment of FIG. 2, the pre-hem slide 29 has a guide member 39 with its longitudinal axis 41 disposed at an angle relative to vertical and being mounted to the assembly 21. An exemplary angle of 55° is shown but other angles may be employed to effect movement of the pre-hem slide 29. The difference between the angle of the guide member 39 and the angle of the tool surface 37 comes into play when angled movement of the slide body 33 causes hemming as explained below.

[0055] The guide member 39 is disposed in an opening such as slot 43 in the slide body 33, with the body 33 having a bore 45 disposed at an end 47 of the slot 43. The bore 45 is sized to receive the guide member when the slide body 33 moves during pre-hemming.

[0056] In this embodiment, the guide member 39 has at least a pair of guide surfaces to control the path of travel of the slide body 33. First, a flat 47 is disposed along the guide member 39, with the flat having a travel distance “X”. The slide body 33 has a heel block 49 disposed in opposing relationship with the flat 47. The guide member 39 also has a surface 51, and the slide body slot 43 has a complementary and opposing surface 53. This configuration controls the path of travel of the pre-hem slide as explained below.

[0057] Finally, the slide body 33 is supported by a rail and bearing assembly 55 to allow horizontal movement of the slide body 33 when appropriate. The assembly 55 is supported by a moveable upper press platen 59. The assembly 55 has a rail 61 that provides a track for roller bearings 63. The bearings 63 are linked to the slide body 33 via members 65, with the rail 61 linked to the platen 59 via members 67.

[0058] The platen 59 is moved by a drive 60 capable of providing the forces necessary for both pre-hemming and final hemming, and movement occurring in the direction shown by arrow “C”.

[0059] Disposed generally opposite the main die 31 and panels 23 and 25 is a final hem die holder 69 that supports the final hem tool 71. The die holder 69 is shown linked to the platen 59 such that the movement of the platen 59 will move both the die holder 69 as well as the slide body 33. Alternatively, the die holder 69 could be driven separately from the slide body 33 using another drive. In yet another mode, each of the slide body 33 and the die holder 69 could be linked to the same drive using a coupling or clutch-type mechanism so that one or both could be selectively engaged to travel. This mode, allows for independent movement of the slide body and die holder without the need for separate drives. For example, the slide body 33 could move in its cycle and then the die holder could move in its cycle. It is preferred though that each of the slide body and die holder move together since this speeds the hemming operation and improves productivity.

[0060] Referring now to FIG. 2 and FIGS. 3(a)-(d), an exemplary use of the apparatus 20 as one mode of the inventive method will now be described. In this use, the platen 59 drives both the slide body 33 and the final hem die holder 69 from a start position as shown in FIG. 2. When the platen 59 travels downwardly, the die holder 69 begins to travel downwardly and towards the panels 23 and 25. At the same time, the slide body 33 also begins to move along two paths of travel. First, by reason of the engagement between the flat 47 on the guide member 39 and the heel block 49 on the slide body 39, the slide body travels along a generally vertical path. At a certain point of this vertical travel, the surface 37 of the pre-hem tool 35 contacts the upstanding edge 75 of edge portion 77 of the panel 25. Further vertical travel of the slide body 33 causes the portion 77 to bend towards an upper face of the panel 23, FIG. 3(b), until the surface 37 is parallel to the surface 79 of the portion 77.

[0061] Because the pressure on the upstanding edge 77 is vertically downward, as opposed to prior art mechanisms which apply an arcing or swinging force, the panel 25 does not lift off the die 31, and a smooth undistorted pre-hem is produced.

[0062] Referring to FIG. 2 specifically, the length of the path of travel of the slide body 33 is controlled by the distance “X” and the spacing “Y.” “Y” is measured vertically between the two surfaces 51 and 53. During downward travel of the slide body 33, the surface 53 will approach the stationary opposing surface 51 of the guide member 39. At the same time, the heel block 49 slides along the flat 47 the distance “X.” Once the surface 53 engages surface 51, the path of travel of the slide body 33 will angle along the longitudinal axis 41 of the guide member 39. In the FIG. 2 embodiment, the slide body 33 will follow a path of travel of 55° from horizontal or 25° from vertical. Controlling distance “X” and spacing “Y” can control the length of vertical travel of the slide body. The greater “X” and “Y” are, the greater the vertical travel distance will be. It is preferred that “Y” approximate “X” so that when the heel block 49 slides off the flat 47, the surfaces 51 and 53 engage to direct the slide body 33 along the angled path of travel. “Y” cannot be less than “X” or a jam may occur by reason that the slide body is being directed vertically by flat 47 and at an angle by surface 51.

[0063] Once the vertical travel of the slide body 33 is terminated, as depicted in FIG. 3b, the bottom portion of the slide body 33 is positioned as shown in phantom line 34 of FIG. 2. Then, the slide body 33 begins to angle away (arrow “D” of FIG. 3b) or retract from the pre-hemmed panel 23, thus exposing the bent edge portion 77 for final hemming. While the slide body 33 is being retracted or angled away by guide member 39, the bearings 63 travel horizontally in the rail 61 (arrow “E”), thus maintaining the horizontal orientation of the slide body 33 as it travels along the angled guide member 39 (or the 45° angle of the surface 37.

[0064] The continued stroke of the platen 59 moves the slide body 33 toward a bottom portion of the space 27, as shown by reference numeral 36 in phantom in FIG. 2. The space 27 should be sufficient to allow the slide body 33 to retract or angle away from the panels without interference by the assembly 21. With the slide body 33 and pre-hem tool moving in the angled or retracted position, the final hem die continues to travel downwardly to contact the pre-hemmed edge 77 as shown in FIG. 3(c) and complete the final hemming operation, FIG. 3(d).

[0065] Although the distances of travel along the vertical path and the angled path can vary depending on the type of hemming operation being performed, an exemplary travel for the vertical distance is about {fraction (3/16)} of an inch. The total vertical travel of the slide body, including travel along both vertical and angled paths is about 1 and ¾ inches. Thus, at the start position of FIG. 2, there should be more than 1¾-inch clearance between the base assembly 21 and the bottom of the slide body 33.

[0066] Once the hemming operation is complete and the final die holder 69 and slide body 33 are at their respective finish positions, the platen 59 is reversed, and the slide body 33 is raised at an angle along the guide member 39 until the flat 47 and heel block 49 meet. The slide body 33 then is raised in a vertical direction until the hemming operation start position of FIG. 2 is attained. Two other panels are positioned in place on the assembly 21 and the hemming operation is performed again. The timing and sequence of the removal of hemmed panels and placement of new panels for hemming can vary, since these steps are not an integral part of the inventive method.

[0067] It should be understood that other known features of hemming apparatus such as devices to hold the panels in place, move panels in place for hemming and remove hemmed panels are well known in the art, and a further description thereof is not deemed necessary for understanding of the invention.

[0068] In addition, it should also be understood that the guide member 39 and its features, and the rail assembly 55 are examples of mechanisms that would guide the slide body 33 along a vertical path, and an angled or retracting path. Other mechanisms achieving or allowing the same movement are within the scope of the invention and can be employed for pre-hemming and final hemming. Further the configuration of that disclosed in FIG. 2 can be altered as well. For example, the guide member could be a rod with a correspondingly dimensioned slot, or the member could be a bar having a square or rectangular cross section. Further, while the guide member 39 is shown disposed within a slot in the slide body and mounted to the base assembly, the guide member could be positioned adjacent and outside the slide body, and the guiding surface 53 could be arranged on an outer surface of the slide body 33 to interact with an opposing surface of the guide member 39. Other mechanisms to guide the slide body along the vertical and angled paths of travel than the pin and bushing type mechanism of FIG. 2 include the use bearings, roller, ball or the like, flat cam slide plates, cam follower type rollers, and the like. Examples are discussed below.

[0069] Similarly, the rail assembly 55 is exemplary of the well known T.H.K. type rails, and other mechanisms that would maintain the horizontal alignment of the slide body during its angled travel could be employed, e.g., guide bars and bushings, wear plate slides and keepers, and the like. Examples of these are also discussed below.

[0070]FIGS. 2 and 3a-3 d are intended to show a pre-hemming operation wherein the pre-hemming action continues when the vertical travel of the slide body stops. This mode is shown in FIG. 4a, wherein the tool 35 is shown in contact with a partially pre-hemmed edge 77 at the point where vertical travel stops. The tool then begins its angled and retractive movement along the hatched lines 42. Since the surface 37 is at a different angle (45°) than the axis of the slide body (55°), surface 37 of the tool 35 continues to contact the edge 77, thus further bending or pre-hemming the edge as shown in hatched lines 44. Eventually, as the surface 37 continues to angle, the portion 77 will achieve the angle of retraction, and the tool 35 will fully retract for final hemming.

[0071] In the mode of FIG. 4b, the guide member 39 is at the same inclination as the tool surface 37 of tool 35, and the tool 35 is shown in the position where vertical travel has ceased. Retraction of the tool 35 along the path 42′ and 42′ produces no further pre-hemming action, the edge 77 has been bent at an angle corresponding to the tool surface 37. Thus, by altering the angle of the guide member 39 and/or tool surface 37, the degree of pre-hemming during vertical travel can change. For example, in FIG. 4b, the angle of the tool surface matches the angle of travel of the slide body so that pre-hemming stops once vertical travel stops. When the slide body angle, θ in FIG. 2, is greater than the angle of surface 37, bending of the upstanding edge can still occur during angled travel of the tool surface 37.

[0072] The angle θ also controls the rate of travel of the slide body 33. The angle of 55° allows the slide body to retract from the pre-hemmed panels at a relatively slower rate, whereas configuring the guide member to a less steep angle, e.g., 45°, causes the slide body to travel at a higher rate during the retractive movement (less distance is covered.)

[0073] It is preferred to do most of the pre-hemming during vertical travel since imparting a downward force on the upstanding edge results in a better pre-hemmed configuration, than using a swinging or arcuate motion as down in the prior art. However, it is also preferred that the slide body move at a more controlled rate wherein the axis 41 of the guide member 39 is at an angle steeper than the angle of the tool surface 37, e.g., 55° for the axis 41 and a 45° angle for the tool surface 37. In this mode, due to the angular difference, the angled movement of the tool surface causes further bending of the upstanding edge.

[0074] In either mode of FIG. 4a or 4 b, the edges are at least partially pre-hemmed during vertical travel of the slide body. Completion of the pre-hemming can occur in the vertical travel mode, or be completed as part of the retraction and angling away of the pre-hem tool to expose the pre-hemmed edges for final hemming.

[0075] As noted above, the inventive method and apparatus is particularly useful for performing a number of hemming operations together. In addition, it is preferred to employ the hemming operation on panels such as hoods, deck lids, doors, and the like that are employed in vehicles such as cars and trucks.

[0076] Referring now to FIGS. 5a-5 e, a cycle is illustrated wherein a cowl, latch and fender sides of a vehicle hood are hemmed. These figures only show those components of the inventive apparatus necessary for understanding of the hemming cycle to be described. The cycle is performed on a first panel 81 that is disposed within a second panel 83, each panel making up the hood. Panel 83 has a pair of upstanding edges 87 and 88, with edge 87 being representative of the edges on the cowl and latch sides, and edge 88 being representative of the fender edges. FIG. 5a shows a pair of pre-hem tools 91 and 93, spaced apart vertically by distance “A.” When the cycle begins, the tool 91 contacts edge 88 with tool 93 still spaced from edge 87. Tool 91 begins the pre-hemming operation in FIG. 5b with tool 93 coming into contact with edge 87.

[0077]FIG. 5c shows that tool 91 is angularly retracted while tool 93 completes the pre-hem on edge 87. During the pre-hemming of edge 87, the final hem tool 95 contacts the pre-hemmed edge 88 to initiate the final hemming step. FIG. 5d shows that while final hemming is at about the 50% completion stage on edge 88, the final hem tool 97 contacts the edge 87. In FIG. 5d, tool 93 is retracted from the edge 87 to permit final hemming of pre-hemmed edge 88.

[0078]FIG. 5e shows the final hem stage wherein each of the final hem tools 95 and 97 flatten the edge 87 to form the desired joint. It should be understood that in the embodiment of FIG. 5, the set of tools 91 and 95 moves as one stroke, and the set 93 and 97 moves as a second stroke. In other words, the pre-hem slide 91 reaches it finish position as its corresponding final hem tool 95 completes the final hemming operation. Likewise, tool 93 reaches its finish position when the die 97 completes its final hemming. The stroke for tools 91 and 95 is completed first, and the stroke for tools 93 and 97 are completed second. Of course, the sets of tools could be positioned with respect to each other and the edges of the panels so that the stroke of each would finish at the same time. For example, the pre-hemming and final hemming of edges 87 and 88 would occur in unison.

[0079] Once the hemming is completed, the tools 91, 93, 95, and 97 would then be raised (either together or in sequence) from the finish position to the start position. Another set of panels would then be positioned on the die, and the sequence would begin again. It should be understood that the use of a pair pre-hem and final hem tools is exemplary, and any number of tools can be employed in combination to pre-hem and final hem a number of panel edges together. While a vehicle hood is exemplified, other parts requiring hemming can also be employed.

[0080] The inventive method entails the use of a pre-hemming step as part of a conventional hemming operation wherein at least a portion of the pre-hemming action takes place with the pre-hemming tool moving in a vertical direction. The pre-hemming can be completed vertically, or vertically and as part of the angular or retractive movement of the pre-hem tool in preparation for final hemming. Final hemming is then performed with the final hem tool being vertically driven against the pre-hemmed edges of the panels.

[0081] In a preferred mode of the invention, pre-hemming is attained by guiding the pre-hem slide using at least one flat surface, and at least one angled surface. Of course, a number of surfaces could be employed depending on the exact configuration of the mechanism employed for guiding of the vertical and angled travel of the pre-hem slide. It is also preferred that the pre-hem slide be maintained in the same orientation during vertical and angled travel so that the angled surface of the pre-hem tool does not change during pre-hem slide travel. This is accomplished in one mode by having the pre-hem slide follow a horizontal rail via bearings during the angled movement. Other modes could be employed as well to maintain the proper orientation of the pre-hem slide.

[0082] Referring now to FIGS. 6a-10, alternative configurations are illustrated for moving the slide body, both vertically and at an angle. FIGS. 6a and 6 b show a guide member 101 having wear plates 103, with the slide body 33 having complementary wear plates 105, and a heel block 106. FIGS. 7a and 7 b show the use of a cam follower 107 rotatably supported by upright 109. The slide body 33 has a pair of wear plates 111, which are configured to contact the cam follower during slide body movement.

[0083]FIG. 8 shows a roller bearing 113 mounted on a pin 115, the pin 115 being supported by bearing supports 117. Again, the slide body has a pair of wear plates 119 for contact with the bearing 113 during slide body travel.

[0084]FIG. 9 shows an alternative horizontal motion mechanism wherein the slide body 33 employs guide bar bushings 121 to slid along the rail 123. The bushings are mounted in guide bar bushing mounting and retaining blocks 125 that extend from the slide body 33.

[0085]FIG. 10 shows another mechanism employing side keepers and hold downs. It should be understood that in this embodiment, the travel path of the slide body 33 is such that the protrusions 131 travel within the side keepers/hold downs 135 and against wear plates 137 situated between the slide body 33 and the upper platen 59 (perpendicular to the plane of the drawing). In each of the embodiments of FIGS. 6a-10, the slide body 33 travels in the same manner as described for FIG. 2. As stated above, the mechanisms depicted in FIGS. 6a-10 are exemplary of those mechanisms capable of controlling the travel path of the slide body in the vertical, angled, and horizontal directions, and mechanisms other than those shown can be employed without departing from the invention.

[0086] FIGS. 11-18 depict other embodiments of the invention.

[0087] These embodiments employ a unique pre-hem slide arrangement that is adapted for not only press hem applications but table top use as well. The table top embodiment differs from the press hem embodiment in that in a press hem, the pre-hem die and the main die are driven by an overhead drive. In a table top operation, the final die is fixed, and the pre-hem die moves only to facilitate final hemming and hemmed panel removal. The drive for the table top embodiment is below the main die. Another difference is that the guide member that helps control the movement of the pre-hem slide is vertically arranged, and the rail and bearing assembly that mounts the pre-hem slide in relation to the upper platen or die fixture is angled with respect to vertical.

[0088]FIG. 11 schematically depicts a press hem apparatus 200, which employs a drive or power source (not shown) similar to that shown in FIG. 2. The drive moves the upper platen 201 up and down along posts 204. Common to both versions of the new embodiment is an angled rail and bearing assembly 203. The rail and bearing assembly 203 is preferably mounted at a 45 degree angle to the tool fixture 205 that is supported by the upper platen 201. This angle could vary, e.g., up to 15 degrees either way depending on the hemming operation. For example, if the panels to be hemmed are not horizontal (tilted upwardly at the hem area), the angle could be increased. Alternatively, the angle could be decreased if the lower pre-hem angle is desired. This assembly is similar to assembly 55 in its use of rollers and rails, and a further description is not deemed necessary for understanding of this aspect of the FIG. 11 embodiment.

[0089] The main die 207 supports the panels 23 and 25, and the fixture 205 supports the final hem die 209. The pre-hem die 211 is supported by the pre-hem slide 213.

[0090] The pre-hem slide 213 can employ a flat cam surface or a machined trough or track to control its travel. FIG. 11 shows a track 215, which is sized to receive the roller 217 mounted on the guide element 219. The guide element 219 rests on base 221, which is linked to the main die 207.

[0091] Still referring to FIG. 11, guides 251 and 253 are provided to assist in the alignment of the tools 209 and 211 during hemming. The guide element 219 is mounted on a push-pull bar assembly 257, which permits the guide element 219 to be positioned with respect to its support 221. These assemblies are well known in the art and do not require a further description for understanding of their operation.

[0092] Referring to FIGS. 12a-c, the hemming operation of the apparatus 200 is as follows. It should be understood that this schematic uses a flat surface rather than a track to control movement of the pre-hem slide 213. Once the panels 23 and 25 are in place, the upper platen 201 is driven from the start position of FIG. 12a so that the pre-hem tool 211 performs the pre-hem as shown in FIG. 12b. While the pre-hem slide 213 is traveling downward, the roller 217 approaches the surface 212. At the point where pre-hemming is complete, the roller 217 contacts the surface 212, see FIG. 12b. The spacing between the pre-hem slide and roller is configured so that contact occurs when the pre-hem operation is complete. When using a track as shown in FIG. 11, track is sized so that when the pre-hemming operation is complete, the roller 217 contacts guide surface 219. When using a track or flat surface, further downward movement of the upper platen 201 and tool fixture 205 causes the pre-hem slide to move horizontally with respect to the panels, and at an angle with respect to the tool fixture 205, see FIG. 12c.

[0093] It is also preferred to use a biasing mechanism as a spring or the like to better maintain the pre-hem slide 213 in place. FIG. 11 shows a spring 218 that is positioned between the tool fixture 205 and pre-hem slide 213. An even more preferred mode is the use of a Datco constant pressure nitrogen spring 218′ as shown in FIG. 14 below. Of course, other means for biasing such as the contact surface(s) employed in FIG. 2 could also be used to keep the pre-hem slide in the proper vertical alignment.

[0094] The hemming angle can be controlled by the relationship between the guide element 219, the pre-hem slide 213 and mounting angle of the pre-hem die thereon as shown in FIGS. 13a-c. In FIG. 13a, by increasing the angle a beyond horizontal, e.g., 20 degrees, the rate at which the pre-hem slide 213 moves can be accelerated such that the pre-hem die 211 can reach into the main die 207 and still retract before final hemming. In this configuration, the angle β is about 30 degrees. FIG. 13b shows a typical pre-hem operation wherein the angle a is around 45 degrees. In FIG. 13c, the angle β is about 60 degrees for use when the panel has a short flange length and an additional squeeze may be desired. FIGS. 13a-13 c show the pre-hem slide 213 with a flat contact surface 212 as depicted in FIGS. 12a-c. At noted above, this surface contrasts with the track 215 in FIG. 11, but each have a common guide surface, 219 or 212. The angulation of the surface 212 or 219 controls the direction of pre-hem travel after pre-hemming is finished. If the surface is horizontal, then the pre-hem slide will move horizontally after pre-hemming. If the surface is angled as in FIG. 13a, the pre-hem slide 213 will angle upwardly when it slides along the rail assembly 203. The configurations shown in FIG. 13a-c could also be employed in the embodiment of FIG. 14 below.

[0095] In the press hem embodiment of FIG. 11, the tool fixture 205 can be made of a one piece cast ring, with the ring supporting a number of final dies and pre-hem slides and surrounding the hemming area. The bottom of the press hem would be the main die with the panels. The middle section would comprise the tool fixture or upper platen that supports the dies. A top support holds the drive that moves the upper platen 201, using four posts 204 as guides, with each post located in a corner. Generally, for a press hem, the upper platen 201 moves between 24 and 36 inches so that there is sufficient room to remove and replace panels.

[0096] An exemplary table top apparatus 300 is shown in FIG. 14.

[0097] While the pre-hem slide 213 and rail assembly 203 are the same, the power source and drive (represented by the arrow 301) are below the main die 207. Since the power source and force are arranged below the main die, the stroke is more limited, 3-8 inches. Therefore, there is not enough room to easily move the hemmed panels or position new panels for hemming. Accordingly, it is preferred in the table top arrangement to have the upper platen or tool fixture 303 that supports the final die 213 and pre-hem slide 213 move or index laterally between start and stop positions. That is, once hemming is complete and the main die 207 lowers to its start position, the tool fixture 303 would index outwardly so that the hemmed panels can be removed and a new set of panels can be positioned for the next hemming operation. The indexing can be achieved using an index cam 307, or a separate drive could be employed to move the tool fixture 303 between operative and retracted positions. A roller system 309, wear plates or similar means can be employed to facilitate the indexing of the upper platen. The roller system 309 has rollers 314 that are mounted for travel along the main die ring 312. The system 309 also employs guide rollers 311 guiding the cam 307 during its indexing. A stop 356 mounted to the main die ring 312 is also provided to control lateral movement of the tool fixture 303.

[0098]FIG. 14 also shows a spring pad holddown 371 and guides 373 and 374, which assist in alignment of the tools during hemming. As with the FIG. 11 embodiment, the guide element 219 and index cam 307 are supported on the main die 207 via push pull bar assemblies 375.

[0099]FIGS. 15a-d schematically depict how the table top hemming apparatus works using the index cam 307. In FIG. 15a, the tool fixture 303 is laterally retracted with respect to the main die 207 in its start position. The main die 207 is driven so that it is vertically raised by a power source (not shown but conventional). This movement causes the rollers 311 of the tool fixture 303 to ride along angled cam surfaces 315 of the index cam 307. The vertical movement of the main die 207 causes the fixture 303 to move laterally towards the panels 23 and 25, with rollers 314 facilitating movement with respect to the main die ring 312, see FIG. 14.

[0100] In FIG. 15b, the rollers 311 of the tool fixture 303 has passed the cam surfaces 315, and no further lateral movement of fixture 303 takes place with continual upward movement of the main die. The main die 207 continues to elevate so that the pre-hemming operation takes place by contact between the panels 23 and 25 and the pre-hem die 211, see FIG. 15c.

[0101] At the time pre-hemming is complete, the roller 217 contacts the surface 212 of the pre-hem slide 213 and the pre-hem slide moves horizontally as the main die 207 continues to rise vertically. With the pre-hem die 211 out of the way, final hemming can take place by contact between the pre-hemmed panels and the final die 209.

[0102] After hemming, the main die 207 retracts and the pre-hem slide 213 and tool fixture 303 move laterally away from the hemmed panels to arrive at the position of FIG. 15a. With the lateral movement of the tool fixture 303 back to the start position of FIG. 15a, the hemmed panels 23 and 25 can be removed and new panels can be positioned for another hemming operation.

[0103] A schematic of a RH door hemming fixture is depicted in FIG. 16. The main die ring 312 surrounds an inner main die 207. Positioned around the main die 207 are eleven pre-hemming and hemming tools (not shown), with a corresponding number of tool fixtures 303, and index cams 307. As explained below, this type of hemming fixture can be easily swapped out for a LH door hemming fixture. Also while not shown, the tool fixture 303 can be secured to the main die ring 312 using box type keepers, or THK rails, or any other equivalent securing means. These help keep the movement of the tool fixture 303 true when moving laterally from the start position to the hemming position, and back to the start position.

[0104] The table top embodiment employs a simplified press arrangement. Unlike press hems wherein the drive is above the hemming area, the table top embodiment employs the drive or power source below the hemming area. In this arrangement, the hemming fixture, i.e., the structure that supports the various hemming components, including the tool fixture, hemming tools, and main die, is moveable for engagement or disengagement with the power source for hemming. With this, the hemming fixture can be removed and replaced with another fixture. For example, a right hand door fixture can be installed for a first hemming operation. Then it can be moved and replaced with a left hand door fixture. At the same time, the panels can be moved into the hemming area in a direction perpendicular to the travel of the fixtures to facilitate the overall layout of the operation.

[0105]FIGS. 17 and 18 show a schematic and an exemplary arrangement for hemming fixture movement. The hemming fixture 403 slidingly supports the tool fixture 303, and fixes the main die in place for hemming. The fixture 403 is held in place by pin 401, clamp 408, and support structure 420. To move the fixture 403, the pin 401 is retracted from the recess 404 in the hemming component 406 and the clamp 408 is pivoted about axis 405 using the cylinder 407.

[0106] Referring to FIG. 18, another cylinder 90 is provided that can move the fixture 403 in the direction “X”. When changing hemming operations, the cylinder 90 would move the fixture 403 in the direction “X” (perpendicular to the view shown in FIG. 17) to staging area B, and pull another fixture to align with the power source 60 from staging area A, or vice versa. The main die 430 rides on rails when it is not supported by the power source 60. With a new hemming fixture in position, the pin 401 and clamp 408 are activated to secure the new hemming fixture in place for another hemming operation. This arrangement is advantageous in that right-hand door hemming fixture can be easily moved out and replaced with a left hand door fixture.

[0107]FIG. 17 also shows wear plates 431 to allow for relative movement between the fixture component 406 and the tool fixture 303. These wear plates are an alternative to the rails shown in FIG. 14 and explained above.

[0108]FIG. 18 also shows the cylinders 407, clamps 408, and pins 401 of FIG. 17, all of which all cooperate to secure the hemming fixture 403 in place. It should be understood that the fixture 403 is not shown in FIG. 18.

[0109] It should be understood that the alternatives disclosed for FIGS. 1-10 apply to the embodiments of FIGS. 11-18, and vice versa. For example, wear plates can be used in place of rollers, both for movement of a given tool fixture as well as interaction between the pre-hem slide 213 and the guide element 219.

[0110] Although not illustrated, the embodiment of FIGS. 1-10 could be used in a table top arrangement, wherein the main die would move vertically, and the pre-hem slide would move in an angled fashion with respect to the vertically moving pre-hemmed panels.

[0111] As such, an invention has been disclosed in terms of preferred embodiments thereof which fulfills each and every one of the objects of the present invention as set forth above and provides new and improved hemming assembly and method of hemming.

[0112] Of course, various changes, modifications and alterations from the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. It is intended that the present invention only be limited by the terms of the appended claims. 

What is claimed is:
 1. In a hemming apparatus adapted to join an upstanding edge of a first panel to an edge of a second panel, the improvement comprising a vertically driven main die supporting the first and second panels for hemming, a tool fixture supporting a pre-hem tool and a final hem tool, the pre-hem tool mounted for angled movement with respect to the tool fixture, a guide mechanism mounted to the main die, the guide mechanism directing the pre-hemming tool in a generally horizontal direction or at an angled upward direction via first and second guiding surfaces after pre-hemming to expose the pre-hemmed panels for final hemming.
 2. The apparatus of claim 1, wherein the main die has a second guide mechanism mounted thereto that is in engagement with the tool fixture, the second guide mechanism moving the tool fixture in one direction to position the pre-hem and final hem tools for hemming, and a second position to expose a portion of the main die for removing hemmed panels and inserting other panels for hemming.
 3. The apparatus of claim 1, further comprising a hemming fixture supporting the tool fixture and the main die, the hemming fixture movable with respect to a power source vertically driving the main die.
 4. The apparatus of claim 1, wherein the pre-hem tool is mounted on a pre-hem slide, the pre-hem slide being mounted at an angle to the tool fixture, the pre-hem slide having the first guiding surface, and the guide mechanism having the second guiding surface, contact between the first and second guiding surfaces moving the pre-hem slide either generally horizontally or at an upward angle for final hemming.
 5. The apparatus of claim 4, further comprising means for biasing the pre-hem slide in place during pre-hemming.
 6. In a method of pre-hemming and final hemming an upstanding edge of a first panel to an edge of a second panel, the improvement comprising at least partially pre-hemming the edges together by first directing a main die supporting the upstanding edge and the edge generally vertically against a pre-hemming tool, and then moving the pre-hemming tool away from the edges in either a generally horizontal direction or a direction upwardly angled to expose the pre-hemmed edges for final hemming.
 7. The method of claim 6, wherein a final die hemming tool is stationary during pre-hemming and final hemming.
 8. The method of claim 6, wherein a guide mechanism mounted to the main die travels vertically with the main die and the pre-hemming tool is slidably mounted at an angle to a tool fixture, upward movement of the main die after pre-hemming directs the pre-hemming tool horizontally away or at an upward angle away from pre-hemmed panels for final hemming.
 9. The method of claim 6, wherein the pre-hemming and final hemming tools move laterally in one direction to a pre-hemming position, and move laterally in an opposite direction after final hemming.
 10. The method of claim 6, wherein a hemming fixture is supporting the pre-hemming tool and final hemming tool is moveable with respect to a power source that vertically drives the main die.
 11. In a hemming apparatus adapted to join an upstanding edge of a first panel to an edge of a second panel and employing a vertically driven final die holder, the improvement comprising a pre-hemming tool holder supporting a pre-hem tool and a mechanism to first guide the pre-hemming tool holder along a generally vertical travel path for at least a partial pre-hemming of the edges, and then to guide the pre-hemming tool along a generally horizontal path or a path having an upward angle by contact between a stationary guide surface and a surface on a pre-hem slide supporting the pre-hemming tool to expose the pre-hemmed edges for one of final hemming or completion of pre-hemming and final hemming.
 12. The apparatus of claim 11, wherein the pre-hemming tool holder is supported at an angle with respect to a tool fixture supporting a final hem holder and the pre-hemming tool holder.
 13. The apparatus of claim 11, further comprising means for biasing the pre-hemming tool in position during vertical travel of the pre-hem tool holder.
 14. The apparatus of claim 11, wherein the pre-hemming tool holder is supported at an angle with respect to a tool fixture supporting a final hem holder and the pre-hemming tool holder, and further comprising means for biasing the pre-hemming tool in position during vertical travel of the pre-hem tool holder.
 15. In a method of pre-hemming and final hemming an upstanding edge of a first panel to an edge of a second panel, the improvement comprising at least partially pre-hemming the edges together by first guiding a pre-hemming tool generally vertically against the upstanding edge, and then moving the pre-hemming tool either horizontally or at an upward angle away by contact between a guide surface on a pre-hem slide supporting the pre-hemming tool and a stationary guide surface to expose the pre-hemmed edges for one of final hemming or completion of pre-hemming and final hemming.
 16. The method of claim 15, wherein the pre-hem slide moves at an angle with respect to a tool fixture supporting the pre-hem slide.
 17. The method of claim 15, wherein the pre-hem slide is biased in place during the pre-hemming operation.
 18. The method of claim 15, wherein the pre-hem slide moves at an angle with respect to a tool fixture supporting the pre-hem slide, and the pre-hem slide is biased in place during the pre-hemming operation. 